As for Sony Vegas, it's because of a file type, I guess? You can't open a MKV/FLV file with Sony Vegas and most of match videos are in MKV these days. To open mp4, you may need to install a plug-in(?). I often meet those messages even with an AVI file for some reasons. I assume it's some sort of codec problem. In other words, SV is getting kinda useless for tennis video editing.